Digital representations

We use somewhat different notation when dealing with digital signals. First, an integer n is used instead of t for the time axis, where n is related to t by the sample period  

Secondly, it is common to use normalised frequency, rather than natural frequency. From 10.28 we see that the relationship between frequency, angular frequency and normalise angular frequency is 

Using n and normalised angular frequency m makes calculations easy as the equations are the same regardless of sample rate. To convert to real frequency, die normalised frequency is simply multiplied by the sample rate. In general, we use the same terms for amplitude and phase 

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